HVAC systems typically contain a heat exchanger system that houses combustion of a gas and air mixture. Typically, air and gas are mixed and ignited within a combustion chamber. Flames from the combustion heat the combustion chamber and may also extend out of the combustion chamber into heat exchanger tubes or clamshells. Air may be blown past the tubes or clamshells in order to be heated. The combustion creates high temperatures within the combustion chamber and the heat exchanger. The high temperatures can cause stresses on the burner and heat exchanger components. There can also be safety or fire risks when components are raised to such high temperatures.
In order to reduce pollutants some HVAC systems implement low nitrous oxide burners and heat exchangers. One typical low NOx system comprises a premixer and/or premix burner. These components mix gas and air prior to combustion in the combustion chamber. Such systems results in higher temperatures than normal systems, in some embodiments up to around 1300 F. With such high temperatures, combustion chambers and heat exchangers can be subject to great stresses, especially in regions between areas of differing temperatures. One solution in the prior art has been to add insulation within the burner. Insulation helps lower temperatures on the surface of HVAC components, but insulation can also direct the heat to different locations within a burner or heat exchanger, merely relocating problems to different locations. Some insulation can also be environmentally damaging.